The present invention relates to valves to dispense products from pressurized containers, and more particularly to aerosol tilt valves operated by angularly tilting the tilt valve stem by finger pressure on the portion of the stem shaft extending above the aerosol mounting cup.
In a known construction of an aerosol tilt valve assembly, a hollow stem discharge shaft is mounted in a resiliently deformable sealing gasket at the top of the container, the stem shaft extending both outwardly from and inwardly into the container through the gasket. The portion of the stem discharge shaft extending outwardly from the container has an axial or lateral outlet, and the portion of the stem shaft extending into the container has at least one lateral inlet metering orifice. When the valve is actuated by tilting, product flows from the container into the lateral inlet orifice, up the hollow stem shaft, and out the axial or lateral outlet.
Further in this known construction, the tilt valve has a substantially conical stem cup provided under the sealing gasket having an outer circumferential edge that normally fully engages the under surface of the sealing gasket inside the container. The cup and the sealing gasket define an annular space surrounding the stem shaft, which space is connected to the hollow interior of the stem shaft by the lateral inlet metering orifice. The stem cup, by virtue of its outer circumferential edge normally engaging the under surface of the sealing gasket, usually prevents product flow from the aerosol container into the aforesaid annular space and into the stem shaft inlet orifice. However, when finger pressure is applied to the stem shaft extending above the mounting cup, the outer circumferential edge of the stem cup is partly disengaged from the surface of the sealing gasket. Product from the container (under the action of propellant) then flows between the disengaged outer circumferential cup edge and the gasket into the aforesaid annular space, then through the inlet metering orifice, up the stem shaft, and is dispensed from the stem shaft outlet. When the finger pressure is removed from the stem shaft, the outer circumferential edge of the stem cup again fully engages the sealing gasket. The aforesaid annular space and inlet orifice are then cut off from the product in the container. In such known construction, a spring also is used to bias the stem cup, particularly its outer circumferential edge, against the sealing gasket.
One of the difficulties of the above-described known construction is that the lateral inlet metering orifice is very difficult to form if the stem shaft and stem cup are of one-piece construction. To be effective, that orifice must be fully within the annular space surrounding the stem shaft and defined by the sealing gasket and stem cup. In other words, the metering orifice must lie below the sealing gasket and the top of the stem cup. In order to conventionally form the inlet orifice, a special tool has been inserted down the top of the hollow stem shaft to punch out the metering orifice from inside the shaft; or a special tool has been inserted through the bottom of the stem during molding to form the metering orifice, the bottom of the stem thereafter being closed. Alternatively, because of the limited space between the cup wall and the stem shaft, a drill had been extended at an angle over the circumferential edge of the stem cup to drill a downwardly extending angled inlet orifice into the stem shaft. All of these operations for forming the metering orifice are less than satisfactory for reasons of complexity and/or controllability of the metering orifice.
It is likewise desirable in tilt valve assemblies of the above general construction to have the stem shaft and stem cup in fixed position with one another for lateral and vertical stability and controllability of the tilt valve operation. The shaft and cup may be made of one piece, in which event there are the aforementioned difficulties in connection with forming the inlet metering orifice. However, if the shaft and stem cup are formed in two separate pieces, subsequently connected together, a permanent assembly operation to prevent disassembly on operation is required in which the two parts must be carefully positioned with respect to each other and locked together to prevent significant movement with respect to each other when the tilt valve is operated. This is difficult to obtain in practice, however. When the stem shaft and stem cup are separately molded of a desirable material such as nylon, which is hygroscopic, and subsequently assembled, the swelling of the assembled parts in their environment may result in disassembly of the shaft and stem cup. Further, if the two separate pieces are not carefully designed, operation of the assembled tilt valve may dislodge the stem shaft from the stem cup.
The present invention is intended to provide an aerosol tilt valve of the above general construction, having at least one lateral inlet metering orifice which is easily formed and can be carefully controlled in size. Further, the stem shaft and stem cup are formed by a method which results in an integral stem shaft and stem cup functioning essentially as a one-piece unit having no possible relative operational motion or possibility of disassembly with respect to each other. In the method of the present invention, the stem shaft is first molded from plastic, the hollow shaft being closed at its base and having an annular recess in its exterior wall adjacent the base of the stem shaft. Slightly above the annular recess, at least one precise lateral inlet metering orifice is easily molded at the same time through the side wall of the stem shaft. A plastic stem cup is then molded about the stem shaft. Normally this would be thought to be difficult to accomplish because of the presence of the metering orifice in the afore described annular space between the stem cup, stem shaft and sealing gasket. Obviously, the molding of the stem cup must not result in refilling the inlet metering orifice. However, by utilizing a particular shape of shield placed over the inlet orifice, which shield also surrounds the stem shaft and further acts as a portion of the molding cavity for molding the stem cup and creating the aforementioned annular space, a unique method of obtaining the desired tilt valve stem construction results. When the stem cup is molded about the stem shaft, an annular, inwardly extending, projection of the stem cup is molded into the annular recess in the exterior wall of the stem shaft. When the shield is retracted, and the remainder of the molding cavity for the stem cup is removed, a fully integrated and very strong tilt valve results with the stem cup and stem shaft locked together essentially as one piece by the molding, and a controlled lateral inlet metering orifice extending into the stem shaft in the aforesaid annular space between the stem cup and stem shaft. The stem cup and stem shaft also have no possible relative movement with respect to each other upon operation of the valve, and a precisely controlled tilt valve results. Further, the molding of the stem cup projection into the stem shaft recess avoids swelling of a nylon shaft and cup creating disassembly, since the nylon cup and nylon shaft swell as one piece.